Separator means, particularly centrifugal separator means, are already known for separating mixtures of metal chips from oil, such mixtures being produced for example by lathe and/or other machine tool operations. An example of such a machine is disclosed in U.S. Pat. No. 4,137,176, assigned to the same assignee as is the present disclosure, entitled "Chip Discharge for Continuous Chip Wringer". Another generally similar separator is shown in the U.S. Pat. No. 3,850,814. Such machine provides a rotary separator having upwardly diverging sides with a perforated zone intermediate the upper and lower edges thereof. A mixture of chips and oil fed centrally into said rotor moves upwardly along said walls in response to centrifugal force, the oil moving outwardly to suitable receiving means through the perforated zone and the chips doing likewise to other receiving means over the upper edge of said rotor. To assist in conveying the chips to the receiving means for same, said rotor is preferably supplied with impeller means for drawing a strong stream of air into such centrifuge and driving it outwardly with said chips as at least a partial carrier for same.
Such equipment operates very well and has received good commercial acceptance. However, it often happens that bar ends, finished parts or other large pieces of metal are included in the mixture of chips and oil as same is introduced into the separator. If said pieces of metal are very large, as they often are, same will seriously damage the rotor of the centrifuge and will often do so very quickly. This has posed a dilemma of either (1) inspecting the mixture prior to introducing same into the separator and removing therefrom such large pieces of metal, which procedure is economically impractical, or (2) submitting to frequent shutdowns and often repairing of the centrifuge as a result of such large pieces of metal entering thereinto. This dilemma has inhibited the commercial acceptance of the separator as above described from what might otherwise be possible and previous solutions for same have not been fully satisfactory.
Air classification in the metal chip conveying art is known, particularly prior to a crusher as shown in a publication of National Conveyors Company, Inc., Bulletin C-1-67, entitled "National ChipVeyors for Metal Chip Processing and Oil Reclamation". However, this system is very complicated and expensive and, therefore, has had very limited use in combination with centrifugal separator means. The reason for this is that the potential for severe damage to a crusher is much greater than it is for other components in the chip conveying system.
Accordingly, the objects of the invention include:
1. To provide inexpensive classification means for removing large pieces of metal from a mixture of such pieces of metal, metal chips and liquid prior to the introduction of said metal chips and liquid into means for separating the liquid and metal chips from each other.
2. To provide inexpensive classification means, as aforesaid, which is compatible with a system in which a large quantity of air is caused to enter into the separating means and expelled therefrom as at least a partial carrier for said chips.
3. To provide inexpensive classification means, as aforesaid, which will be relatively simple and can be applied to equipment of an existing design by relatively minor modification thereof.
4. To provide inexpensive classification means, as aforesaid, which will have a high degree of reliability and will maintain said reliability over a long period of time with a minimum of maintenance.
5. To provide inexpensive classification means, as aforesaid, which will not interfere with the proper operation of the means separating the liquid and chips from each other.